QoS Differential Scheduling of URLLC Under FIFO Service Discipline: A Cross-Layer Approach

Ultra-reliable and Low-latency Communication (URLLC) has the potential to support data traffic transmission in factory automation, telesurgery, and automatic driving, where the differential quality of service (QoS) requirements in different types of traffic should be considered. In this letter, a differential QoS oriented URLLC policy is investigated for achieving high energy-efficiency under the given delay tolerance. To characterize the system state, a queueing model under First-In-First-Out (FIFO) service discipline is implemented. Based on this model, a cross-layer approach is developed to analyze the average transmission power and delay by formulating the system state into a Markov chain. For solving the problem more efficiently, the states of similar behavior in the Markov chain are aggregated, based on which the approximate solution can be obtained with low complexity. Numerical results verified the theoretical analysis and good performance of the proposed approach.